Conductance and Kondo Effect in a Controlled Single-Atom Contact

Néel, N.; Kröger, J.; Limot, L.; Palotás, Krisztián; Hofer, Werner A.; Berndt, Richard

doi:10.1103/physrevlett.98.016801

Cited by 176 publications

(211 citation statements)

References 31 publications

(25 reference statements)

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“…Scanning tunneling microscopy (STM) offers the possibility of building a well-defined single-atom contact exhibiting the Kondo effect [28], which may be tuned through a tip displacement [29]. Here, we use a nickel tip to contact an individual Co atom adsorbed on a Cu(100) surface (see inset of nized to be a spin-1/2 Kondo system [30,31].…”

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Kondo Resonance of a Co Atom Exchange Coupled to a Ferromagnetic Tip

et al. 2016

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The Kondo effect of a Co atom on Cu(100) was investigated with a low-temperature scanning tunneling microscope using a monoatomically sharp nickel tip. Upon a tip-Co contact, the differential conductance spectra exhibit a spin-split asymmetric Kondo resonance. The computed ab initio value of the exchange coupling is too small to suppress the Kondo effect, but sufficiently large to produce the splitting observed. A quantitative analysis of the line shape using the numerical renormalization group technique indicates that the junction spin polarization is weak.

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Kondo Resonance of a Co Atom Exchange Coupled to a Ferromagnetic Tip

et al. 2016

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“…In this range, one typically detects a Kondo resonance for magnetic adatoms [2,12], which is due to the interaction of a spin-state at a magnetic impurity with the conducting electrons of the underlying metal. Kondo resonances have a very characteristic signature, described by a Fano function [13,14,15]:…”

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Creating pseudo-Kondo resonances by field-induced diffusion of atomic hydrogen

2008

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In low temperature scanning tunneling microscopy (STM) experiments a cerium adatom on Ag(100) possesses two discrete states with significantly different apparent heights. These atomic switches also exhibit a Kondo-like feature in spectroscopy experiments. By extensive theoretical simulations we find that this behavior is due to diffusion of hydrogen from the surface onto the Ce adatom in the presence of the STM tip field. The cerium adatom possesses vibrational modes of very low energy (3-4meV) and very high efficiency (≥ 20%), which are due to the large changes of Ce-states in the presence of hydrogen. The atomic vibrations lead to a Kondo-like feature at very low bias voltages. We predict that the same low-frequency/high-efficiency modes can also be observed at lanthanum adatoms.Scanning tunneling microscopy and spectroscopy (STM/STS) are at present the main tools to analyse the behavior of single atoms and molecules at conducting surfaces. Experiments at very low temperaturestypically around 4-5K -have contributed considerably to our understanding of single atom contacts [1], Kondoresonances and their signature in the near-contact regime [2], spin-flip excitations of single atoms and atomic chains [3,4], and vibrational excitations of single molecules [5]. Recently, the changes of electronic properties or atomic configurations due to field excitations were thoroughly investigated in STM experiments [6,7,8]. The salient feature in these experiments is the ability to modify the systems by varying the position and the field-intensity of the STM tip. However, the electronic properties of atoms can also be modified by the presence of hydrogen, as e.g. the measurements of Gupta et al. showed for nominally clean Cu(111) surfaces [9]. They obtained spectroscopic data with negative differential resistance, characteristic of vibrational excitations of a molecule [10]. Hydrogen itself, which is quite ubiquitous in a low-temperature ultra-high vacuum (UHV) environment, can only rarely be resolved in STM experiments [11]. Its effect on experimental scans has so far not been studied in great detail.The aim of this Report is to demonstrate the ability of manipulating the position of atomic hydrogen at the nanometer scale by the field of an STM tip and to determine its effect in spectroscopy experiments at very low bias voltages. In this range, one typically detects a Kondo resonance for magnetic adatoms [2,12], which is due to the interaction of a spin-state at a magnetic impurity with the conducting electrons of the underlying metal. Kondo resonances have a very characteristic signature, described by a Fano function [13,14,15]:with ǫ = (eV − ǫ 0 )/Γ. In this equation, A is the amplitude coefficient, B is the background dI/dV signal, q is the Fano line shape parameter, ǫ 0 is the energy shift of the resonance from the Fermi level due to level repulsion between the d-level and the Kondo resonance, and Γ is the half width of the resonance.In recent low-temperature experiments M. Ternes [16] found that adsorption of cerium ato...

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“…It is now possible to tackle nontrivial many-body effects in a controlled environment. The Kondo resonance has been investigated through scanning tunneling microscopy (STM) in single atoms either isolated [2][3][4] or coupled to other atoms, [5][6][7][8] in single-atom contacts, [9][10][11] and in single molecules. [12][13][14][15][16] It has also been successfully evidenced in nanoscale devices, [17][18][19][20][21] in particular quantum dots, [17][18][19][22][23][24] carbon nanotubes, [25][26][27] and nanowires.…”

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Nonequilibrium spin-current detection with a single Kondo impurity

et al. 2013

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We present a theoretical study based on the Anderson model of the transport properties of a Kondo impurity (atom or quantum dot) connected to ferromagnetic leads, which can sustain a nonequilibrium spin current. We analyze the case where the spin current is injected by an external source and when it is generated by the voltage bias. Due to the presence of ferromagnetic contacts, a static exchange field is produced that eventually destroys the Kondo correlations. We find that such a field can be compensated by an appropriated combination of the spin-dependent chemical potentials leading to the restoration of the Kondo resonance. In this respect, a Kondo impurity may be regarded as a very sensitive sensor for nonequilibrium spin phenomena.

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Conductance and Kondo Effect in a Controlled Single-Atom Contact

Cited by 176 publications

References 31 publications

Kondo Resonance of a Co Atom Exchange Coupled to a Ferromagnetic Tip

Kondo Resonance of a Co Atom Exchange Coupled to a Ferromagnetic Tip

Creating pseudo-Kondo resonances by field-induced diffusion of atomic hydrogen

Nonequilibrium spin-current detection with a single Kondo impurity

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